The arm rest according to EP 1,164,051 has primary and secondary parts with surfaces centered on a common axis (center axis), confronting each other, and formed like a jaw clutch with face teeth, the primary part mounted on the arm-rest body being pivotal and also axially movable.
The latch teeth of EP 1,164,151 having blocking and sliding flanks like Hirth teeth or a jaw clutch make it possible is with fairly small primary and secondary parts to withstand substantial angular load moments. In addition this known arm rest makes it possible for a control device to determine at what angular positions the primary and secondary parts mesh so that downward pivoting of the arm-rest body is blocked in the selected positions.
The control device for this arm rest is two cam bumps on the primary part. More particularly a control ring between the primary part and secondary part is rotationally coupled to the primary part and carries the two radially projecting cam bumps in diametrally opposite locations. The control ring formed as a separate part can, according to requirements, be better designed, e.g. by being formed integrally with the primary part.
To resist greater torque loads, EP 1,164,051 optimizes the face teeth of the primary part and secondary part in that the teeth of the primary part and of the secondary part are each formed as annularly continuous rings which can therefore be made so big that the outer periphery of the circular area corresponds to the outer periphery of the cross sections of the primary part and/or secondary part with the teeth extending around the entire circumference of the primary part and secondary part. In order to block downward movement of the arm-rest arm, all the teeth, that is a multiplicity of teeth, mesh.
The dependence of the control ring on the pivotal movement of the arm-rest body in the known arrangement is eliminated over a small angle in that the primary part has two circular-segmental slots open in its plane toward the secondary part in each of which a cam bump projecting from the control ring toward the primary part engages and which cooperate with a stationary cam track of the secondary element. In this manner each cam bump of the control ring is of a smaller angular dimension than the respective slot of the primary part. As a result of the different angular dimensions of the slots (large) and cam bump (small) the primary part both in the lowered position and at the start of upward pivoting as well as in the raised position and at the start of downward pivoting of the arm-rest body has some play before engagement of the cam bumps with the first or second end faces of the respective slots.
In EP 1,165,051 a compression spring coaxial with the secondary part and primary part presses the primary part fixed on the arm-rest body axially against the secondary part. The axial shiftability of the primary part is limited by a plate-shaped abutment fixed on the common central axle. Thus the compression spring is effective via a particular pressure-distributing plate on the tooth-free outer end of the primary part which creates a relatively bulky and expensive construction.
In the arm rest according to EP 1,164,501 there is also the disadvantage that with a small upward adjustment of the arm-rest body which is coupled to the axially movable primary part creates a small axial movement of the arm-rest body which can be a problem in close quarters.
In order to prevent damage to such an arm rest the maximum load should not exceed for example 80 daN. It is even preferable to provide a margin of safety and to set up the arm rest with an overload protector that responds at about 30 daN, that for example decouples the toothed structure so that when the load limit is exceeded the arm-rest body can be deflected downward to a position determined by a vehicle-body abutment. Such an overload protector is generally described for example in German 2,714,581.